1. Field of the Invention
The present invention relates to thermostatic controls for regulating the temperature in an area such as a house, office or the like and in particular to such a control which will automatically control a heating or air conditioning system to regulate the temperature therein at at least two different temperatures at selected times and for selected periods of time.
2. Description of the Prior Art
Thermostatic controls for controlling the heating and/or air conditioning systems of homes, offices, and other buildings to regulate the temperature therein are well known. Typically, such thermostatic controls are electro-mechanical devices which automatically cycle the furnace, air conditioning unit, and related equipment between "on" and "off" states to thereby maintain the temperature within the area within prescribed temperature limits. The regulated temperature is determined by manual setting of a "set point" device on the thermostatic control whereby the temperature can be regulated within a couple of degrees over a range of about 50.degree.F to 90.degree.F. The thermostatic control is typically mounted on a convenient wall within the dwelling, office, or the like and is coupled to the furnace or air conditioning unit via permanent wiring installed within the walls thereof.
Recently, the need for conserving energy has emphasized the value of such a thermostatic control which will automatically alter the regulated temperature within the area at different periods of the day in accordance with required "comfort" requirements. For example, it has been determined that the temperature in a home can be reduced significantly at night when the occupants are asleep without causing any discomfort. Such a reduction in the "nighttime" temperature of the dwelling results in a significant reduction in fuel consumption and heating (or cooling) cost for the dwelling.
However, manual alteration of the regulated temperature is not entirely satisfactory inasmuch as the dwelling, office or the like will be uncomfortably cool in the morning before it is manually reset and, due to the lag time of typical heating systems, time is required for the temperature of the dwelling to rise to a comfortable level for the normal daytime activities. Similarly, manual alteration of the regulated temperature at night may result in uncomfortably cool temperatures within the dwelling before the occupants have fallen asleep.
The need to manually alter the regulated temperature is of course always subject to the human failure of foregetting to change the thermostat setting at all whereby cost savings are lost.
Recently, there have been introduced energy conserving thermostats which will automatically regulate the temperature of a home, office, or the like at two different temperatures. These devices typically include some form of clock mechanism and means for setting the two selected operating temperatures. In a normal cycle, the energy conserving thermostat automatically reduces the regulated temperature of the dwelling at predetermined times of the day and automatically returns the temperature of the dwelling to the other of the regulated temperatures again at a selected time of day. Prior art energy conserving thermostats have, however, had some limitations inasmuch as they require rewiring of the heating and/or air conditioning system to accomodate the dual temperature thermostat. Such systems have also been typically electro-mechanical in nature whereby their versatility is limited and also requiring unnecessarily large amounts of power for their operation. Such devices are also prone to common failures of electro-mechanical systems.